Hydraulic system for single engine truck crane or the like

ABSTRACT

A hydraulic system for a single engine truck crane includes a pump input section in the carrier that is driven by the carrier engine and an output section in the upper works. A closed loop connects the input and output sections and requires only two passages through the swivel joint. The working reservoir is in the upper works, and a supercharge pump in the upper works is driven by the output section and draws from the reservoir to feed the loop. In one embodiment the output section comprises a flow divider leading to valve units and working motors which are incorporated in the closed loop, and in another embodiment the output section includes a power motor which is driven by the pump in the carrier and which drives working pumps in the upper works that serve the working motors.

United States Patent Grider et al.

1451 Aug. 29, 1972 [54] HYDRAULIC SYSTEM FOR SINGLE ENGINE TRUCK CRANEOR THE LIKE [73] Assignee: Bueyrus-Erie Company, South Milwaukee, Wis.

[22] Filed: April 14, 1971 [2i] Appl. No.: 133,799

3,550,506 12/1970 Gardenhour ..9l/4l4 Primary ExaminerEdgar W. GeogheganAttorney-Allan W. Leiser, Arthur H. Seidel and John Adams ThierryABSTRACT A hydraulic system for a single, engine truck crane includes apump input section in the carrier. that is driven by the carrier engineand an output section in the upper works. A closed loop connects theinput and output sections and requires only two passages through theswivel joint. The working reservoir is in the upper works, and asupercharge pump in the upper works is driven by the output section anddraws from the reservoir to feed the loop. In one embodiment the outputsection comprises a flow divider leading to valve units and workingmotors which are incorporated in the closed loop, and in anotherembodiment the output section includes a power motor which is driven bythe pump in the carrier and which drives working pumps in the upperworks that serve the working motors.

9Clains,2DrawingFigures R ETRACT EXTEND POlNT RAISE LOWER RAISEBACKGROUND OF THE INVENTION This invention relates to truck cranes orsimilar machines of the type in which a single engine in a carri erserves also as a prime mover for operating elements in an upper worksrotatably mounted on the carrier, and particularly to an improvedhydraulic system for such a machine.

Conventionally, truck cranes and similar mobile machines have twoengines, one in the carrier and one in the upper works. It is, however,advantageous at least in some cases to provide a single engine machinein which the carrier engine also serves as a prime mover for the upperworks. Among other things, this eliminates the need for two separateengines and fuel systems, and the operator is more isolated from enginenoise.

I-Ieretofore, single engine machines have generally had working pumpsfor the upper works elements located in the carrier and driven directlyby the carrier engine, and the multiple output lines from the pumps arefed upwardly through a multi-passage swivel joint between the carrierand upper works and thence to the operating elements. This sort ofarrangement, however, has several serious disadvantages. First, theseveral pumps which are necessary in most machines take up considerablespace in the carrier, and this presents a particular design problemwhere standard carriers are purchased and used. Second, since bothpressure and return lines must lead through the swivel joint, the swiveljoint becomes extremely long and expensive; and it is difficult tohandle and repair and presents designs problems because of the verticalspace required. Third, the working fluid reservoir must be located inthe carrier where it presents additional space problems, and where theweight of fluid in the reservoir cannot be used advantageously as acounterweight for the upper works. These problems are of courseparticularly serious in large machines.

SUMMARY OF THE INVENTION The general object of this invention is toprovide a hydraulic includes for a single engine machine including apump inlet section in the carrier, an output section in the upper works,and a closed loop connection between the two which requires only twopassages through the swivel joint, the working fluid reservoir beingdisposed in the upper works for advantageous weight distribution. In thepreferred embodiments, a supercharge pump in the upper works is drivenby the output section in what amounts to a feedback action and drawsfluid from the reservoir to supply losses in the closed loop. In oneembodiment of the invention, the output section includes a flow dividerand the operating valves and working motors are incorporated in theclosed loop, and there are special provisions for compensating for thedifferences in fluid requirements as working cylinders extend orretract.

The system of the invention is extremely simple and relativelyinexpensive while still being highly efficient, and it offers numerousdesign advantages. Since only a pump section need be in the carrier,standard carrier designs can easily be used, and it is also relativelyeasy to modify the upper works to substitute a separate engine, thusallowing the same basic design to be used for both single and dualengine machines.

Other objects and advantages will appear from the description to follow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagramillustrating a first embodiment of the invention incorporating a flowdivider output section, and

FIG. 2 is a schematic diagram which is similar to FIG. 1 but which showsanother embodiment in which the output section includes a power motorwhich drives working pumps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, thereference numeral 1 indicates the deck of a conventional carrier and thenumeral 2 indicates the floor of a conventional revolving frame or upperworks which is revolvably mounted on the carrier by means of aconventional bearing 2' and is hydraulically connected to the carrierthrough a standard swivel joint 3. As indicated, the carrier 1 can be ofany conventional type, it being a particular advantage of this inventionthat any of a number of standard carrier designs can be used withoutextensive modification. The upper works 2 will of course mount suitableoperating elements, which in the case of a truck crane will include aboom with raising and extending mechanisms, a swing mechanism to revolvethe upper works 2, and a hoist mechanism, all powered by double orsingle acting cylinders or other hydraulic motors, one of which is shownschematically as 18'. While the particular embodiments shown areintended for truck cranes, however, it will be apparent that theinvention is applicable to any machine with a carrier and a revolvingupper works which mounts operating elements. Swivel joints which providefor hydraulic passages between a carrier and upper works are also wellknown, and the swivel joint 3 may be of any suitable type. Since thegeneral construction and operation of truck cranes is well known tothose skilled in the art, and since the invention has other equallyobvious applications, a detailed showing and description of the elementsthus far referred to is unnecessary and has been omitted for the sake ofsimplicity and clarity.

A standard engine 4 is located in the carrier and powers the carrier andthe upper works as will be described. The engine 4 is fitted with anysuitable type of power take-off unit 5, and thus serves to drive a pumpinput section, which in this embodiment is a set of two gear pumps 6suitably placed in the carrier, although one or more pumps could be useddepending on requirements. A pressure line 7 leads upwardly from thepumps 6 and a return line 8 leads downwardly to them, and these linespass through the swivel joint 3. It is a particular advantage of theinvention that only the two lines 7 and 8 need pass through the joint 3.

Since the engine 4 powers the upper works, it must be controllable by anoperator seated therein. To this end, a throttle cable 9 leads from theupper works to the carrier through the swivel joint 3, this being accomplished by means of a pivoting linkage l0 and a ball swivel 11. Theremust also be electrical connections between the carrier and upper works,and this can be accomplished through any suitable type of conventionalelectrical swivel joint, indicated schematically by a the referencenumeral 12.

The reference numeral 13 designates a flow divider which constitutes theoutput section of the hydraulic system in this embodiment. Flow dividersare also well known to those skilled in the art, and can be consideredessentially as a group of pumps with a common inlet, which is shownschematically as the terminus 7 of the line 7. In the presentembodiment, there are three pumps l4, l and 16 which serve separatevalve units as will be described. Flow from all of these ultimatelyreturns to a point 17 which can be considered to define the upperterminus of the return line 8 as a unitary element.

The pump 14 serves a valve unit 18 made up of a bank of three standard,interconnected, manually operated directional control valves 19, andincluding two pressure relief valves 20. The pump serves a valve unit 21made up of three more manually operated, interconnected directionalcontrol valves 22 and a pressure relief valve 23. The pump 16 serves avalve unit 24 which includes a single manually operated directionalcontrol valve 25 and a pressure relief valve 26. The valve units 18, 21,24 serve of course to feed pressure fluid to and accept return fluidfrom the working motors for the operating elements (not shown). Again,the particular elements and functions are not relevant to the inventionas such, and so the functions have simply been indicated on the drawingsin a manner which makes them readily understandable to those skilled inthe art. It should be noted, however, that the valve units have closedloop connections with their associated cylinders or other motors so thatall fluid flowing from the valve units is ultimately returned to themand thence to a common return as will be described.

Fluid from the pump 14 moves to the valve unit 18 through a line 27, andall of the return fluid leaves the valve unit 18 through a line 28 whichleads through a filter unit 29 to the point 17. The valve unit 21 isserved through a line 30, and all return fluid from the unit 21 leavesthrough a line 31 which joins the line 28 at point 32. The valve unit 24is served by a line 33, and return fluid moves through an intermediatereturn line 34 which includes a heat exchanger 35 and which terminatesat the point 17. A fan 36, which is suitably driven by the flow divider13, operates to cool oil passing through the heat exchanger 35. Whileonly a portion of the total oil flow is thus cooled, this is sufficientto maintain the total system temperature at desired levels.

A main pressure relief valve 37 is connected between the pressure line 7and the return line 28, to protect against excessive overall systempressures.

Since the valve units 18, 21 and 24 all have closed loop connectionswith their working motors, they and their motors can be considered to beincorporated in a completely closed loop which, in essence, leads fromthe pumps 6 through the line 7 to the flow divider 13, through the valveunits and motors to the point 17 and thence through a common return line8 to the pumps 6. Since this is a closed loop system which does not drawdirectly from a reservoir, some provision must be made to replaceunavoidable oil losses and maintain acceptable inlet pressures at thepump 6, and this is accomplished by means of a supercharge pump 38 whichis also suitably driven by the flow divider 13. An inlet line 39 for thepump 38 leads from a working oil reservoir 40 which is located in theupper works. An output line 41 leads from the pump 38 and joins the line28 at point 42, which is on the return side of the loop. A superchargerelief line 43 leads from the line 28 to the reservoir 40 and includes apressure relief valve 43 which is set and serves to limit the outputpressure of the pump 38. Fluid passed through the relief valve 43' movesthrough a filter unit 44 back to the reservoir 40. A check valve 39' isconnected between the lines 39 and 28, and this allows the pumps 6 tosuck oil from the reservoir 40 during start-up to prevent cavitation;the valve 39 being closed when supercharge pressure builds up.

Since the system will usually involve a number of double acting singlerod hydraulic cylinders as working motors, such as the cylinder 18,there can be a significant difference in flow rates depending uponwhether the cylinders are being extended or retracted. When thecylinders are being extended the input flow is significantly greaterthan the return flow because of the cylinder rods, and when they arebeing retracted the return flow is significantly greater. In onecommercial design, for example, there is a net difference ofapproximately gallons between the requirements for movement of allcylinders from full retraction to full extension and movement from fullextension to full retraction, and some means must be provided tocompensate for this difi'erential. In the embodiment shown, this isaccomplished by the pump 38 and a second relief valve 45 which isconnected in parallel with the valve 43 and is set to open at a somewhathigher pressure. The capacity of the pump 38 is such that, duringextension when more fluid is moving out from the flow divider 13 than isbeing returned through the line 8, it can supply the difference from thereservoir 40. During retraction, when excess fluid is being returned,the valve 45 will open and pass the excess to the reservoir 40. Whilethe valve 43' could theoretically serve both to limit the pump 38 and todispose of excess fluid during retraction, it is difficult to provide asingle relief valve which can accommodate such widely varying flowrates, and using the second valve 45 set to open at higher pressure is ahighly advantageous method.

It is important to note that all working fluid for the system issupplied by the reservoir 40 which is in the upper works. Not only doesthis make it unnecessary to provide reservoir space in the carrier 1,but the reservoir 40 can easily be located in the upper works in aposition where the weight of the fluid serves as an additionalcounterweight.

Referring now to the embodiment of FIG. 2, the carrier deck isdesignated by the reference numeral 46, 47 designates the upper works,47 is the bearing, and 48 designates the swivel joint. An engine 49operates through a power take-off 50 to drive a single pump 51 whichconstitutes the input section of the hydraulic system. A pressure line52 leads from the pump 51 through the swivel joint 48, and a return line53 leads back through the joint 48 to the pump 51. A throttle cable 54controls the engine 49 through a linkage 55 and a ball swivel 56. Anelectrical swivel connection is indicated schematically at 57. Theelements 46 through 57 correspond, respectively, to the elements 1through 12 in the embodiment of FIG. 1, except that the terminalconnections for the lines 52 and 53 are different and the input sectionis a single pump-although multiple pumps could be used.

The pressure line 52 in this embodiment leads directly to a power gearmotor 58 in the upper works, and the return line 53 leads back from thepower motor 58 through a filter unit 59 to the pump 51, there being as aresult a simple closed loop connection between the pump 51 and powermotor 58, the power motor 58 serving as an output section which suppliespower to working pumps. A system relief valve 60 is connected across thelines 52 and 53 to limit overall system pressure. Again, it is importantto note that the lines 52 and 53 represent the only hydraulicconnectionsbetween the carrier and upper works, so that the swivel joint 48 needhave only two hydraulic passages.

The power motor 58 drives a working pump section 61 made up in this caseof three working pumps 62, 63, and 64. The pumps 62-64 correspond,respectively, to the pumps 14-16 in the embodiment of FIG. 1, and servevalve units 65, 66, and 67 which correspond, respectively, to the valveunits 18, 21, and 24 of the embodiment of FIG. 1. In this embodiment,however, the working pumps and valve units are not incorporated in theclosed loop, and the pumps 62-64 draw from a common working fluidreservoir 68 which is in the upper works. A common return line 69returns all fluid to the reservoir 68 through a filter unit 70. A checkvalve 53' is connected between the reservoir 68 and line 53 to preventcavitation during start-up, and is closed when supercharge pressure isbuilt up.

The valve unit 65 includes three valves 71 and two pressure reliefvalves 72. It is supplied by a line 73 leading from the pump 62, and allreturn fluid is fed into the line 69 at point 74. The valve unit 66includes three valves 75 and a pressure relief valve 76; and it issupplied by a line 77 leading from the pump 63 with return fluid movinginto the line 69 at point 78. The valve unit 67 includes a valve 79 andpressure relief valve 80; it is supplied by a line 81 from the pump64and return fluid flows into the line 69 at point 82. Again, all of thevalves are manually operated directional control valves which controldouble or single acting cylinders or other working motors, one of whichis shown at 65', and the particular functions are indicated on thedrawing.

A supercharge pump 83 is also driven by the power motor 58 and drawsfrom the reservoir 68. An output line 84 leads from the pump 83 andconnects to the return line 53 at point 85, the pump 83 thus serving toreplenish losses in the closed loop. A heat exchanger 86 in the line 84faces a fan 87 which is also driven by the power motor 58, thisproviding a cooling of a portion of the system oil to maintain theentire system temperature at a desired level. To compensate for extraoil introduced into the closed loop by the pump 83, there is a pressurerelief valve 88 which is connected between the lines 53 and 69.

Other than the fact that the valve units and working motors are notincluded in the closed loop circuit, the embodiment of FIG. 2 offers thesame advantages as the embodiment of FIG. 1. Only two passages throughthe swivel joint 48 are necessary, the supercharge pump 83 is driven bythe output section of the system to have a feedback type of action, andall of the working fluid for the system is supplied by the singlereservoir 68 which is located in the upper works and can be desirablylocated to provide an additional counterweight.

It is important to note that both. embodiments only a power take-offunit and a pump section of one or a few pumps need be located in thecarrier, and this makes it extremely easy to accommodate the system tostandard carrier frames. In both cases, it would be relatively easy toreplace the output section with a separate engine occupying the samespace, so that the same basic design can be used for either single ordual engine machines. The systems are highly effective and yetrelatively simple and inexpensive.

Although two preferred embodiments of the invention have been shown, itwill be obvious that other embodiments and variations in application andstructure are possible without departure from the spirit of theinvention. The invention is not, therefore, to be limited by the showingherein or in any other manner except as may specifically be required.

We claim:

1. A hydraulic operating system for a truck crane or the like includinga carrier with an engine, an upper works revolvably mounted on thecarrier and a hydraulic swivel joint interposed between the carrier andupper works, said system comprising:

a pump input section mounted in the carrier and driven by the engine; anoutput section in the upper works; a closed hydraulic loop connectingthe input and output sections, the loop including a single pressure lineleading from the input section through the swivel joint into the upperworks and a single return line leading from the upper works through theswivel joint to the input section; a fluid reservoir in the upper worksthat supplies substantially all of the working fluid for the system; anda super charge pump that draws from the reservoir and serves to pumpfluid into the closed loop.

2. A hydraulic operating system according to claim 1 wherein thesupercharge pump is in the upper works and is driven by the outputsection. and pumps fluid into the closed loop at a point in the upperworks.

3. A hydraulic operating system according to claim 2 wherein: the upperworks includes a plurality of control valve units with each unit adaptedto have a closed loop connection with at least one working motor and tosupply all pressure fluid to and receive all return fluid from theworking motor; and the output section comprises a flow divider connectedto the pressure line; and there are a plurality of outputs from the flowdivider which lead to respective valve units; and return fluid from allof the valve units enters "the return line in the upper works; and anoutput line from the supercharge pump leads to the return line.

4. A hydraulic operating system according to claim 3 wherein: at leastone valve unit serves at least one working motor which is a doubleacting cylinder that requires more fluid for extension than forretraction and returns more fluid during retraction than duringextension; and the supercharge pump is adapted to supply the extra fluidrequired for extension; and there is a relief line leading from thereturn line to the reservoir which includes pressure relief valve means,the pressure relief valve means serving to limit the output pressure ofthe supercharge pump and to dispose of excess fluid entering the returnline during retraction.

5. A hydraulic operating system according to claim 4 wherein thepressure relief valve means includes two pressure relief valves inparallel, one of which opens at a certain predetermined pressure tocontrol the output pressure of the supercharge pump and the other ofwhich opens at a higher predetermined pressure to dispose of excessreturn fluid.

6. A hydraulic operating system according to claim 3 wherein: there is acooling fan in the upper works that is driven by the flow divider; andthere is an intermediate return line leading from one of the valve unitsto a point on the return line which includes a heat exchanger facing thefan.

7. A hydraulic operating system according to claim 2 wherein: there isat least one working pump in the upper works which draws from thereservoir; and the output section comprises a hydraulic power motorwhich is driven by the input section and which drives the working pumpand the super charge pump.

8. A hydraulic operating system according to claim 7 wherein: the upperworks includes a plurality of valve units; and there are a correspondingnumber of working pumps all driven by the power motor, one working pumpserving each valve unit.

9. A hydraulic operating system according to claim 8 wherein: an outputline leads from the supercharge pump to the return line and includes aheat exchanger; and there is a fan in the upper works which is driven bythe power motor and faces the heat exchanger.

1. A hydraulic operating system for a truck crane or the like includinga carrier with an engine, an upper works revolvably mounted on thecarrier and a hydraulic swivel joint interposed between the carrier andupper works, said system comprising: a pump input section mounted in thecarrier and driven by the engine; an output section in the upper works;a closed hydraulic loop connecting the input and output sections, theloop including a single pressure line leading from the input sectionthrough the swivel joint into the upper works and a single return lineleading from the upper works through the swivel joint to the inputsection; a fluid reservoir in the upper works that suppliessubstantially alL of the working fluid for the system; and a superchargepump that draws from the reservoir and serves to pump fluid into theclosed loop.
 2. A hydraulic operating system according to claim 1wherein the supercharge pump is in the upper works and is driven by theoutput section and pumps fluid into the closed loop at a point in theupper works.
 3. A hydraulic operating system according to claim 2wherein: the upper works includes a plurality of control valve unitswith each unit adapted to have a closed loop connection with at leastone working motor and to supply all pressure fluid to and receive allreturn fluid from the working motor; and the output section comprises aflow divider connected to the pressure line; and there are a pluralityof outputs from the flow divider which lead to respective valve units;and return fluid from all of the valve units enters the return line inthe upper works; and an output line from the supercharge pump leads tothe return line.
 4. A hydraulic operating system according to claim 3wherein: at least one valve unit serves at least one working motor whichis a double acting cylinder that requires more fluid for extension thanfor retraction and returns more fluid during retraction than duringextension; and the supercharge pump is adapted to supply the extra fluidrequired for extension; and there is a relief line leading from thereturn line to the reservoir which includes pressure relief valve means,the pressure relief valve means serving to limit the output pressure ofthe supercharge pump and to dispose of excess fluid entering the returnline during retraction.
 5. A hydraulic operating system according toclaim 4 wherein the pressure relief valve means includes two pressurerelief valves in parallel, one of which opens at a certain predeterminedpressure to control the output pressure of the supercharge pump and theother of which opens at a higher predetermined pressure to dispose ofexcess return fluid.
 6. A hydraulic operating system according to claim3 wherein: there is a cooling fan in the upper works that is driven bythe flow divider; and there is an intermediate return line leading fromone of the valve units to a point on the return line which includes aheat exchanger facing the fan.
 7. A hydraulic operating system accordingto claim 2 wherein: there is at least one working pump in the upperworks which draws from the reservoir; and the output section comprises ahydraulic power motor which is driven by the input section and whichdrives the working pump and the supercharge pump.
 8. A hydraulicoperating system according to claim 7 wherein: the upper works includesa plurality of valve units; and there are a corresponding number ofworking pumps all driven by the power motor, one working pump servingeach valve unit.
 9. A hydraulic operating system according to claim 8wherein: an output line leads from the supercharge pump to the returnline and includes a heat exchanger; and there is a fan in the upperworks which is driven by the power motor and faces the heat exchanger.